Described below is a valve for opening and closing a flow channel in a lab-on-a-chip system The valve is defined by a support body which has at least one first recess in the form of a flow channel and has a second recess directly next to a subregion of the first recess, as is known for example from EP 0 180 064 B1.
In biosensor technology, lab-on-a-chip systems are used in order to be able to carry out biochemical analyses in parallel. Microfluidic instruments and a chip having an array of sensors are integrated on a support, which may be, for example, a plastic card. The array of sensors may be, for example, electrochemical sensors which are arranged in columns and rows on the chip. The sensors are coated with molecules, to which the substances to be detected bind specifically. The specific binding is detected electrochemically by changes in current and/or voltage. In this way biochemical substances, for example antibodies, peptides or DNA, can be detected in solutions to be examined, for example blood or urine.
The measured electrochemical signals may be processed directly by integrated circuits on the chip, or they may be read out from the chip by an external evaluation unit. The chemicals required for the examination may be delivered from the external evaluation unit to the support or they may already be on the support, for example in the form of dry reagents. During the examination, the solutions, i.e. liquids, are delivered to the support and fed on the support via microchannels into a reaction chamber. The chip with the sensor array is located in the reaction chamber.
Reactions required for the detection may take place in the microchannels and/or the reaction chamber.
In the case of complex biochemical reactions which are required for the detection, the fluid flow of the solution must be controlled. For instance, it may be necessary for the liquid to stay for a predetermined period of time in a region of the microchannels, so that for example dry reagents which are stored in this region are dissolved and chemical reactions take place. Only after completion of the chemical reactions is the liquid fed further through the microchannel. Furthermore, when detecting biochemical substances in the reaction chamber it may be necessary to close the reaction chamber in a fluid-tight fashion. To this end, valves are to be provided in the support. They are to be arranged at particular selected positions in the support, for example in the inlet and outlet of the reaction chamber.
EP 0 180 064 B1 discloses valves, which are designed to close microchannels. The microchannels are arranged in a first support, which is covered with a thin membrane on the side of the microchannels. The thin membrane is arranged in a sandwich fashion between the first support and a second support. Arranged in the second support, there are plunger-like instruments which can be pressed with the aid of springs via the membrane onto openings of the microchannels in the first support. The microchannels are thereby closed by the membrane. The described valves include a number of individual parts and can only be formed by a system having at least two supports and a membrane. The multiplicity of parts leads to problems with the reliability and leaktightness of these valves. Furthermore, a structure of at least two supports leads to high production costs and elaborate alignment of the plunger-like instruments in the second support over the openings of the microchannels of the first support.